Abstract: In the background of literati gatherings and their poetry recitals and replies using the same rhyme sequence, the Northern-Song-Dynasty poetry underwent a change in its external form and system. There appeared long topic, long foreword, self note in the capacity of explanation and narration to foreshadow, supplement and explain the content of the poem.The poets further pursued lyricism and artistry of the topic and foreward so as to make them complementary to the artistic conception of the poem. The causes for the formation of the four in one are: firstly it is the influence of the creative background of the close contact and frequent gathering of literati, secondly it is the result of the propagation consciousness on the part of the poets and lastly it reflects the influence from the style conception of “respecting the style” and “breaking with the style” of the Song people.